Gas turbines are widely used to convert hot gases into energy, especially electricity. Such turbines basically comprise a plurality of turbine blades positioned on a turbine wheel for rotation as a result of the flow of high pressure gases past the turbine blades to cause the wheel to rotate, thereby rotating a shaft coupled to the wheel to produce energy to drive an electrical generator or the like. The present invention provides improved turbine blades, which result in increased efficiency in such turbines.
In the use of turbines, for the production of electrical energy by the use of hot, high pressure combustion gases to drive the turbine, the turbine blades are typically configured to a clearance of about 0.20 inches between the outer ends or tips of the turbine blades and the inside of the turbine casing or a shroud or block positioned inside the turbine casing in an annular position in the same vertical plane as the rotation of the turbine blades. This clearance is provided to avoid any contact of the blade tips with the inside of the casing, and in many instances is larger than necessary and results in inefficiency in the operation of the turbine. Similarly, many turbine blades are designed so that cooling air flows outwardly through the turbine blades from a turbine blade wheel and is required to flow through the clearance between the turbine blade tips and the inside of the casing. This results in the design of turbine blades with greater than necessary clearance. This results not only in the flow of the cooling air through the clearance gap between the turbine blade tips and the inside of the casing but also permits hot gas to flow through this clearance gap, thereby bypassing the turbine blades and reducing the amount of energy produced in the turbine by the hot gas.
Since fuels for the generation of the hot high-pressure gases required to drive turbines are expensive, a continuing effort has been directed to the development of improved turbines and turbine components to increase the efficiency of the turbines.
According to the present invention, an improved turbine blade is provided. The improved turbine blade is configured for use in a turbine having a turbine case and includes an outer turbine blade tip on the turbine blade, which when positioned in the turbine provides a clearance on a high pressure edge of the turbine blade tip of less than 0.180 inches between the turbine blade tip and an inner diameter of the turbine case, the turbine blade tip containing a rim about at least a portion of an exterior of the tip defining an inner tip surface, and a plurality of air outlets for the discharge of cooling air through the inner tip surface.
The present invention further includes an improved turbine blade configured to mount on a turbine blade wheel in a turbine casing and having a high pressure side clearance from about 0.140 to less than 0. 180 inches between the turbine blade tip and an inside surface of the turbine casing, the turbine blade comprising: a turbine blade base adapted for positioning the turbine blade on a turbine blade wheel and an outer end of the turbine blade comprising a turbine blade tip extending outwardly from the turbine blade wheel toward the inside of the turbine case; an air passageway positioned to supply air to an inner passage in the turbine blade; a first rim positioned along a high pressure side of the turbine blade to provide clearance of the turbine blade tip from about 0.140 to less than 0.180 inches; a second rim positioned along at least a portion of a low pressure side of the turbine blade tip to provide a clearance of at least 0.180 to about 0.200 inches or more; an inner surface area between the first and second rims; and, air outlets through the inner surface area and in fluid communication with the air passageway.
The present invention further comprises a turbine comprising: a turbine blade wheel positioned inside a turbine casing on a rotary shaft and adapted to support a plurality of turbine blades; an air passageway positioned in fluid communication with at least a portion of the turbine blades to supply air to a turbine blade including a turbine blade tip; a first rim along a leading edge of at least a portion of the turbine blade tips; a second rim along at least a portion of a trailing edge of the turbine blade tips; a turbine tip surface defined by the area between the first and second rims; and, a plurality of air outlets from the air passageway through the turbine tip surface, the ends of the first rim defining a clearance spacing between the first rim and the inside of the turbine casing from about 0.140 to less than 0.180 inches.